Had the opportunity to run the ported aluminum Mummert heads on the 312 dyno mule.  I was already in the process or running a variety of iron heads in a single day on the mule engine in preparation of the ‘Exhaust test to end all tests’ and did manage to sneak the ported aluminum heads into this test session. The ported aluminum heads were conveniently off of the EMC engine to make molds of the combustion chambers for a new domed piston design so it was just a matter of bolting them onto the mule for a quick three pull test.  Thanks to Randy Gummelt for spending the day in helping change out several sets of heads while doing the dyno testing.

The mule engine is the +060 over 312 with cast pistons that reside 0.025” in the hole and still retains the same Crower camshaft that’s been used in a multitude of other tests.  1.6:1 roller rockers are being used with Best Gasket head gaskets.  A stock Mummert intake with 750cfm Holley carb atop a 1” spacer is also being used.  377HP with the EMC headers and 368HP with the Sanderson headers.  Here’s the graph showing the ported Mummert aluminum heads on the dyno mule with both the Sanderson 1½” tube headers w/22” of 2½” collector extension/no mufflers and the EMC 1¾” stepped headers with mufflers.

what do you think the compression ratio is of the mule with the aluminum heads?

Thanks for doing this test. I'd hinted before about using the EMC heads on the dyno mule and as John had said that the labor and therefore the cost, would be restrictive for a street engine. It's great to see how well the ported aluminium heads have done over the raw ones. I assume an increase in volumetric efficiency and interesting to see how well they work at lower RPM, as Bill pointed out, the torque figures. It would be interesting to see how well they drove. 

36.4 hp increase at about 1.2 hp per cube is impressive for a run of the mill engine.

Your and John's work with these heads have certainly opened up options in engine upgrades. 

I think I read earlier that John had made changes to the castings and ports of the aluminium heads. the EMC heads being one of the first cast runs. Are there flow figures for raw and street ported and street ported (later casts) for comparison?

Regards

Warren Adams

The production heads have stock gasket openings and 1.94" valves.

I'd also point out that we don't know much about the Crower cam in the Mule. It may have considerable seat timing that might not make it friendly at low RPM and it is close to 240 degrees @.050" putting it toward the upper end of street friendly cams. I can tell you I sell probably 30-40 224@.050" cams for every 240@.050" cam for Y-Block street use.

I'm glad to see the 1-1/2" Sandersons do well. Flow bench testing showed that the exhaust exited the port in a much more confined column than the stock iron heads leading me to believe they would work better with small headers than the stock heads. The iron heads need very large headers to work well, due in large part to the way the exhaust leaves the head.

Thanks Ted for going to this extra effort. This is great information for us and the end users also.

John.  Thanks for the comments.  Always appreciated.

Regarding the Crower cam in the 312 dyno mule, it’s over forty years old!  It was originally purchased by Bob Martin and powered his 312 powered ’56 Merc with a four speed for thirty some odd years on both the drag strip and the street.  At this point that same camshaft is still making noise in the dyno mule.  As John points out, this camshaft is on the big side for your everyday driver but starts to shine where head work has been performed.  On the flip side, the dyno mule has managed to make 292HP with this cam and with the stock G heads on it.  In retrospect, this probably wasn’t the best cam for all the testing that’s been done but the price was sure right as it was sitting in the core engine that was provided in exchange for a new engine build.  Here’s some more detail on that particular Crower camshaft. 

Since the duration at .006" is 291 and the advertised duration is 280 it has a very short lash ramp. Looks like advertised duration was figured at .010 or .011" lift. Most cam grinders nowadays quote advertised duration at .020" lift and would call this a 265 degree cam.

Looks like it was ground 2 degrees retarded if it is installed with a standard timing set.

Nathan, any cam can be ground again. It is difficult to add more than .030-.040" additional lobe lift but what really requires removing a lot of material is changing the lobe separation. If you regrind a stock Y-Block cam with 113 degree separation it can't be changed to a 108 separation. The base circle will get very small. If you try to change the lobe separation and add lift you are asking for trouble. Ted has experimented with small base circles and knows the limit, I have never tried less than 1.200". But then I've haven't made a 4" stroke work. New cams with high lift lobes will take the base circle to less than stock just to clean up. Stock is 1.360".

Nathan.  This is not a reground camshaft.  It’s just an original old and well used Crower camshaft from their older Monarch series of grinds.  Seventies era to be exact.  The lifters being used are still the same ones Bob originally purchased with the camshaft for use in his ’56 Merc and I just made it a point to insure that the same lifters went back on the same lobes they were originally run on.  Based on the age of the lifters, I’ll go out on a limb and say they were made by Johnson.

John.  You’re close on the lash as the spec card calls for 0.016” cold.  That would end up being ~0.014" hot.  The amount of retard that’s present simply reinforces why you degree in a camshaft as opposed to just aligning the marks with twelve pins between them.  Just counting the pins doesn’t tell you much other than the engine will probably crank and run and that's assuming the pins are being counted on the oil filter side of the block and not the other side.

Here’s a scan of the original cam card for this particular camshaft.  Thank Bob Martin for hanging on to this card for all those years.